Traditionally, restaurant food portions have been stored in plastic bags to maintain freshness once the food was divided into individual portions. The object was to prepare the food portions in advance of the actual need (i.e., normally during the slower hours of operation of the restaurant). This allowed for a more efficient use of labor. However, once the food was divided into portions, any freshness markers on the original package were lost. Thus, it became difficult to keep track of the freshness of the food portions after they were formed.
To overcome this drawback of having unmarked portions, labels were applied to the plastic bags. Labels were typically made from colored paper having an adhesive backing. To use the labels, the user had to take a label from a package and apply it to the plastic bag. This method required several steps and therefore was labor intensive. Moreover, the labels could occasionally fall off and defeat the very purpose for which they were used. Further, the use of labels was more costly, since a user had to buy both the plastic bags and the labels.
Another alternative using labels was to preprint the date on the labels. However, the user still had to buy both the plastic bags and labels. Further, the user still had to use additional labor to apply the labels and the labels could still fall off.
An alternative to the labels was to write the date directly on the plastic bag without using a label. The drawback to this approach was that expensive, special purpose pens were needed to mark the bags, so that the ink would not run or rub off. A modification to this alternative, to avoid the expensive pens, involved placing a white substance on the plastic bag to form a writing space which accepted ordinary ink. These sections, if labeled, typically recited "date" or "contents". However, this approach still required the additional labor of marking the bag at the time the portion was formed.